Medication Search: Lice Killing Shampoo

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Lice Killing Shampoo

Common Name:

pyrethrins - piperonyl butoxide


How does this medication work? What will it do for me?

This is a combination medication that contains 2 active ingredients: pyrethrins and piperonyl butoxide. This medication is used to treat head lice and crab lice infestations.

Pyrethrins belong to the group of medications called insecticides. Pyrethrins are naturally occurring insecticides that are extracted from the flowers of chrysanthemum plants. It works by paralyzing and killing lice. Piperonyl butoxide increases the amount of time that the product is effective for by preventing the breakdown of pyrethrin.

This medication should get rid of lice infestation after one application. It may take up to 24 hours for the lice to die after treatment. A second application may be needed 7 to 10 days after the first treatment if you still see live lice.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are using this medication, speak to your doctor or pharmacist.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to use this medication if their doctor or pharmacist has not recommended it.

What form(s) does this medication come in?

Ask your pharmacist or doctor for details.

How should I use this medication?

Do not use any other product in your hair before using this product. This medication should be applied to dry hair.

Soak your hair as well as the skin of the infested area using at least 25 mL of product. If you have thick or long hair, you should use more than 25 mL. Leave the product on for 10 minutes. Work the product into your hair and skin by using small amounts of water to create a lather. Rinse the product out thoroughly. For head lice, comb wet hair with a regular comb to remove tangles. Then, separate a strand of hair no wider than the nit comb and use the nit comb to remove the dead lice and their nits. Wipe off the comb and repeat until all hair has been combed with the nit comb.

Check the hair and remove nits daily for 7 days after treatment. It is recommended that you repeat this process in 7 to 10 days to kill any new lice that may have been hatched since the first treatment. You should not use this product more than 2 times in 24 hours.

Since lice infestations are spread through contact, you should make sure that your family members and sexual partner(s) are examined for lice infestation. If they are infested, they should speak to their doctor or pharmacist immediately about using this product. Also notify your child’s school, daycare, or other people who have been in close contact.

To prevent reinfestation, contaminated items such as bedding, towels, clothing, and hats should be washed in very hot water and dried in the dryer using the hot cycle for at least 20 minutes. If items cannot be washed and dried this way, dry-clean or seal them in a plastic bag for 2 weeks and wash normally. Combs and brushes should be soaked in hot water above 54°C or in undiluted product for 5 to 10 minutes and rinsed with hot water.

If your doctor or pharmacist has recommended a dose different from the ones listed here, do not change the way that you are using the medication without consulting your doctor or pharmacist.

It is important that this medication be used exactly as recommended by your doctor or pharmacist.

Store this medication at room temperature and keep it out of the reach of children. If you have any leftover product, dilute it with water and pour it down the drain. The bottle should be rinsed well and discarded.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Pyrethrins – piperonyl butoxide should not be used by anyone who is allergic to pyrethrins, synthetic pyrethroids, chrysanthemum, ragweed, or to any of the ingredients of the medication.

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • red, irritated, itchy skin

Although most of the side effects listed below don’t happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • redness, swelling around the eyes

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Stop using this product if you experience signs of infection (e.g., skin redness, swelling, warmth, or discharge) or skin irritation (e.g., redness, stinging, swelling, itching, pain) and talk to your doctor or pharmacist.

Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Accidental swallowing: If this product is swallowed, call your doctor or a local poison control centre immediately. Drink a large amount of water or milk. Do not induce vomiting.

Hair and skin application only: This product is for skin and hair application only. This product should not be inhaled and is harmful if swallowed. Avoid contact with the eyes, nose, and mouth. If contact with these areas occurs, rinse them well with lots of water. This product should not be used on eyebrows or eyelashes. If lice infestation occurs on eyebrows or eyelashes, talk to your doctor or pharmacist.

Pregnancy and breast-feeding: If you are pregnant or breast-feeding, you should talk to your doctor or pharmacist before using this product.

Children: The safety and effectiveness of this medication have not been established for children under 2 years of age. Talk to your doctor or pharmacist before using this product on a child under 2 years of age.

What other drugs could interact with this medication?

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. In many cases, interactions are intended or are managed by close monitoring. Speak to your doctor about how any drug interactions are being managed or should be managed.

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Last Updated: 13/07/2024